cbs 5 reporter bob has more on how the morning unfolded. >> reporter: it was a massacre. and most of the victims were first graders. autopsies on the bodies of the children revealed that many, if not all, had been shot multiple times. wayne carver is the chief medical examiner for connecticut. >> i only did seven of the autopsy. the victims i had ranged from three to eleven and i only saw two of them with close-range shootings. >> reporter: investigators believe that most of the shootings came from an assault rifle. it was one of four guns adam lanza took from the home he shared with his mother after he shot and killed her. sources say he left one gun in his car, and then he forced his way into the school, carrying the assault rifle in his hands and two semiautomatic pistols in the dark military-style cargo pants he was wearing. inside the school, he zeroed in on two classrooms, killing 20 children and six adults. one of them was the school's principal, who sources say tried to stop the shooting by lunging at the gunman. the spree ended when lanza shot himself with one of